Most of us, if asked to provide a science-based answer to that question, would be able to offer little more than a shrug. There are many who would quickly turn to God as the explanation - and leave it there. But for a group of super-specialized scientists, those who actually understand things like quantum mechanics and Einstein's theories, the answer may lie 330 feet below ground on the border of Switzerland and France.

What's there is a $9 billion particle accelerator - a 17-mile race track that can send subatomic bits racing about at nearly the speed of light. And then they smash into each other and the real fun begins.

Scientists revved up the device on Wednesday, and the first collisions are to take place next month.

What they'll then have on their hands will be a subatomic wreck - and unimaginable amounts of data about what the collision left behind. The next step? Look at what's there. Think of this phase as similar to an accident reconstruction team, except that instead of looking at skid marks and broken telephone poles, they'll be looking at stuff that's a billionth the size of almost nothing. Or smaller.

They hope to find something they believe to exist, an elusive piece of the physical puzzle. It's got to be there, they believe, because it's a part of their theory of how the universe works. And if it's not? If this massive project, 14 years in the making, turns up nothing new at all? Don't ask. That would send their best theories down the drain. Then, even the world's smartest scientists would be able to do little more than shrug when asked what holds the universe together.

But if they do indeed find something? They will have a better understanding of how things work, how atoms are like stars - and how they are not. And then they can explain it all to the rest of us. In terms we'll understand.

And then? That stuff about the relation between time and space? And bending light? And black holes and dark matter? Maybe all of that - and more - will soon come clear, too.